1. Technical Field
The present invention relates to stators for rotating electric machines that are used in, for example, motor vehicles as electric motors and electric generators.
2. Description of Related Art
There are known rotating electric machines that are used in motor vehicles as electric motors and electric generators. These rotating electric machines generally include a rotor and a stator. The rotor is rotatably provided and functions as a field. The stator is disposed in radial opposition to the rotor and functions as an armature.
Japanese Patent Application Publication No. JP2014147190A discloses a stator for a rotating electric machine. The stator includes an annular stator core and a three-phase stator coil. The stator core has a plurality of slots arranged in a circumferential direction thereof. The stator coil is comprised of three phase windings (i.e., U-phase, V-phase and W-phase windings) that are mounted on the stator core so as to be received in the slots of the stator core and be different in electrical phase from each other. Each of the phase windings is comprised of two sub-windings that are connected parallel to each other. In addition, the phase windings are star-connected with each other to define a neutral point therebetween.
Moreover, there is also known a method of reducing the AC copper loss in such a known rotating electric machine as described above by increasing the number of the sub-windings of each of the phase windings of the stator coil. However, with the winding structure of the known rotating electric machine, it may be difficult to achieve an electrical balance between the parallel-connected sub-windings of each of the phase windings of the stator coil. Consequently, circulating current may be generated in the sub-windings, thereby increasing the electrical loss of the known rotating electric machine.